In laboratories and industrial plants where smoke and fumes may be produced during certain steps of a fabrication process, it is necessary to filter noxious gases and fumes from the air to prevent atmospheric pollution. Such an operation is carried out by specifically designed scrubbing systems, also referred to as scrubbers. Scrubbers purify the gases collected at the various locations where smoke, fumes or other polluting gaseous substances are released. Due to the large investment needed for obtaining efficient scrubbing systems, it is a common practice to select a centralized scrubbing system where suction ducts convey the gas-air mixture. This is particularly applicable when there are numerous locations releasing substances in need of being filtered, as depicted in FIGS. 1a and 1b.
Collection systems include suction ducts that interconnect different suction locations through a branch-like or star-like conduit structure, as shown in FIGS. 1a, 1b and 2. Similar suction systems for recirculation are also present in centralized air-conditioning installations to draw the air from the rooms and provide it to a purification and conditioning station. The suction ducts are often installed on the roofs of buildings, and consequently, they are exposed to intense solar irradiation and other atmospheric agents that may damage the suction ducts through prolonged exposure. It is common practice to use fiber glass reinforced resin pipes or similar corrosion and heat resistant materials capable of resisting attack from chemical substances that may eventually be released in the gaseous mixture conveyed through the suction ducts.
If a fire develops in an air suction area, the flames may reach other suction areas through the collecting conduits that join at the nearest node of the suction system. Furthermore, spreading of the fire may even be aided by the automatic switching off of the suction system. This feature is commonly implemented at scrubbing plants to meet safety rules in case of a fire.